Method of oxidizing asphalts



United States PatentOfiice 2,776,933 Patented Jan. 8, 1957 2,776,933 METHOD OF OXIDIZING 'ASPHALTS Henry G. Gossen', loco," British Columbia, Canada, as-' signorto Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application June 16, 195s," Serial No. 362,143

3 Claims. (Cl. 196-74) The a present invention concerns-animproved process 15 for air-blowing petroleum asphalts. More particularly, it

relates to animproved process for oxidizing residual petroleum stocks" by air-blowing them in the presence of" ferric chloride." The 'present'imp'rovementrelates to the type of ferric chloride employed in the asphalt air blowingoperation and inth'e manner of adding the ferric chlo-' ride to the asphalt. Essentially, thepresent improvement consists in employing ferricchloride-"in the form of FeClsJ6HzO which has been liquefied by heating it above its congruent melting point. In other words, the

FeCls.6H2O

is heated to a temperature such that it dissolves in-its own water of crystallization, and the resulting solution is-then added to an asphalt that-is being oxidized by-a conventional air-blowingprocess.--

The 'production "of oxidized asphalts by blowing air through a petroleumresidue or straight run' asphalt at elevated temperatures is well known in the art of petro leum-refining- It has been establishedthat sucha procedure has a decided effect upon the physical properties of the asphalt. In general, this technique serves'toincrease the hardness, softening point; pliability,rand weathering resistance of an asphalt and decreases its ductilityand susceptibility to changes-in temperature. It

will be noted that the'hardness of a straight run-asphaltmay be greatly increased by extensive steam or vacuum and'thelikew In general, oxidized 'asphalts areavailablehaving softening points of abou't'100 F. to 250 F. or more and penetrations of about 200 down to about 10 (100 g./ 5 sec./ 77 F.).- Bycomparison,'straightreduced asphalts are generally available possessing softening points of about 100 F. to 170 F. and having penetration values of about 200 down to 10'or'20 (100"g.'/5 sec/77 'F.').

In connection with the conventional proces'sof *air blowing petroleum"asphalts', 'it has further been found that certain materialsmay be added to the asphalt being processed which will further modify the physical" proper ties of the final product. For example, it has been esta'lS- lished that compounds such as ferric chloride make pos sible the production of air-blown asphalts having even greater softening points for a given penetration than is possible by air-blowing alone. The use of these materials also greatly reduces the period of time usually required in an air-blowing operation.

As a result of their Up to the present "time, ithas been conventionallpracticein an-"asphalt air blowingoperatfinto add" solid ferric chlorideto an'a sphalt for the purpose ofcatalyzin g the're'a'ction and also for controlling the properties-of thefin'al product. It ha's'further been foundthat solid FeCl3.6H2O appears to 'be somewhafisuperior to other solid forms of ferric chloride 'insuch an operation. This technique, while it is superior" tothe'use "of air alone, still possesses" certain disadvantages. It: has been" ob served that considerable foamin'g generallyoccurs when the solid ferric chloride employed contains any water of crystallization. Furthermore, it has generally been difl'icult to achieve good mixing of the solid ferric chloride with the asphalt with the result that its catalytic effectiveness hasnot' been completely utilized. In addition, theuse ofany" form of ferric chloride adds to the cost of the fin'al product, thus making it desirable to find a method ror'redue'ing'ne amount of this material required for an air-blowing operation.

Accordingly',itis an'objec't of the present invention to provide a method for rapidly and efficiently dispersing ferric chloride throughout an asphalt without undesira ble foaming. It is an additional object of the present inven-' .tion "to provide a means for more "conveniently handling (storin'g 'and' pumping) the-ferric chloride prior to its in trodu'ction within thcasphalti- It is also an object of the prese'nt"invention to use" greatly reduced amounts of ferric chloride in asphalt-blowingoperations"and yet produce' -"oxidized' asphalts possessing "substantially the same penetration softening'-'point"relationships as are now' pro vided by larger amounts of ferric chloride. 7

These and' other object's" of the "present invention may be "achieved by (1) using ferric chlorid'e in thefo'rm' of" FeCl3.6I- I'2O which is conventionally and commercially available in solidform-;""(2)' by heating the solid FeCl3.6H2O

to a temperature suflicient to causeits solutionin its water'of crystallization; and (3) by' introducing 'the resulting liquefied ferric chloride'as such within an asphalt in an air-blowing process. It has been discovered that this technique not only reduces the foaming that is normally-caused by the addition ofsolid FeCl s 6H2O to a hot asphalt, but also greatly-enhances the effectiveness of the ferric chloride in catalyzing the oxidationof theasphalt. For example, it has been established that the amount of FeClaGI-IZO required by'following this pro cedure is about A or less than the amount required by adding'ferric 'chlor'ide'in solidl'form. It has also been found that when the FeCla.6H20 is heated'to' a temperature above'98'F;, the FeCl .6H2O 'dis'solves'in its own water of crystallization and will rerinainfiuid down "to temperatureof about F.- This feature of the present invention makes itpossible to store and pump this materialin the forirl" of a liquid rather-than" as a solid; The benefitsder'ived from" this feature are" well recognize'd'in the art.

In order to bettef describe the present invention, it is feltnecessary to first briefly describe a conventional-process forair-blowing'a petroleum asphalt. Generally speaking", a straight-run *petroleumasphalt stock having the following physical characteristics is suitable for the produetion of 'anoxidized asphalt.- It must be free from wax at a low softening point. The asphalt stock must be of a mixed base or naphthenic type. After oxidation it should have a high penetration for a given softening point. It must be ductile and pliable and resistant to weathering.

The asphalt is heated to a temperature of about 400 to not over 520 F. and is passed to a reaction zone barrel batches in horizontal stills. In addition, this pr cess may be carried out either batchwise or continuously, depending upon the equipment available.

Following the air-blowing operation, the oxidized asphalt is removed from the air-blowing zone or reactor and is pumped to any desired location. In some instances,

EXAMPLE 1 Portions of a straight run asphalt were oxidized under substantially identical conditions of air rate, temperature, asphalt charge, etc. (1) in the absence of ferric chloride, (2) in the presence of liquefied FeCls.6HzO, (3) in the presence of solid FeCls.6H2O and (4) in the presence of solid FeCls. It will be appreciated that the hydrates involved did not necessarily exist as the hydrates after they were added to the asphalt. Each portion of asphalt was oxidized to three levels of softening point, and the penetration of the products measured :in each instance. The results of this study are shown below.

Table 1 Straight Run 0.25% FeChfiHaO 1% FeCh.6H2O 1% FeCh added Asphalt Inspection Asphalt added as a liquid added as a. solid :1 solid Penetration, 100 g./5 see/77F. 38 18 12 60 33 70 35 27 30 23 Softening Point, F 140 170 200 M0 170 200 140 170 200 140 170 200 it may be cut back with diluents such as petroleum naphtha, kerosene, fuel oil, etc. The preparation of cutback asphalts is well known in the art, and it is felt that a detailed description of such an operation is therefore not required here.

When ferric chloride has been added in the past to an asphaltpassing through an air-blowing process, the ferric chloride has been conventionally added in the form of a solid to the asphalt directly within the oxidizing zone. Nothing other than the turbulent condition normally existing within an oxidizing zone has been relied upon to disperse the ferric chloride throughout the reaction mixture.

The present invention modifies the process just described in that liquid FeCl3.6H2O is the particular form of ferric chloride to be employed. As stated earlier, this hydrate is commercially and conventionally available in solid form. In accordance with the present process, this hydrate is heated to a temperature above 98 P. whereupon the ferric chloride dissolves in its own Water of crystallization. This phase of the present process may be carried out in any conventional corrosion-resistant type of vessel such as a steam heated autoclave, electrically heated vessel, or the like.

Once liquefied, the ferric chloride may be stored in conventional corrosion-resistant storage tanks in liquid form down to temperatures of about -80 F.

The ferric chloride solution may be added to the hot asphalt either within the reactor or within the transfer line through which the asphalt flows to the reactor. It is preferred that the ferric chloride be added to the asphalt within the transfer line but either method may be used. Better contact and mixing is generally obtained by addition of the catalyst to the transfer line. Usually 1% or less by weight is all the catalyst that need be added. The liquid ferric chloride is preferably added at its ambient temperature (100 F.) by pumping it into the transfer line as charging of the reactor progresses and at a rate calculated to obtain uniform mixing. Agitation may additionally be obtained by air-blowing. Blowing time may vary somewhat, depending upon the nature of the asphalt stock, the design of the apparatus, the relationship of penetration and softening point desired, etc.

The following example serves to better describe the present process and to illustrate the benefits that are derived therefrom.

As demonstrated in the table above, the use of ferric chloride makes possible the production of oxidized asphalts that are beyond the reach of the straight air-blowing process. In addition, the table clearly brings out the ability of the present process to utilize very much smaller amounts of ferric chloride than are conventionally required under substantially identical reaction conditions. In other words, the effectiveness of the ferric chloride is greatly increased.

It will be appreciated that the present process may be modified in various respects without departing from the scope or spirit of the invention. For example, asphaits derived from cracking operations may be processed in a manner similar to straight-run asphalts. In addition, the present oxidation process may be combined with distillation steps to produce asphalts of a wide combination of properties, or residues that have been distilled further than desired may be blended with heavy petroleum distillates before oxidation.

What is claimed is:

1. In the oxidation of a petroleum asphalt by blowing the asphalt with air in the presence of ferric chloride, the improvement which comprises extraneously liquefying FeCls.6H2O by heating it above its congruent melting point and adding up to about 1 weight percent of the resulting liquid to the asphalt being oxidized.

2. In a process for preparing an oxidized asphalt wherein the asphalt is transported through a conduit to a contacting zone and wherein the asphalt is then contacted with air in the presence of ferric chloride in a conven tional manner, the improvement which comprises extraneously melting FeCl3.6HzO and incorporating within said asphalt less than about 1.0% by weight of said melted FeCl3.6I-I2O.

3. Process as defined in claim 2 in which the FeCl3.6HzO is introduced within the asphalt as it is transported through the conduit.

Properties of Asphaltic Bitumen (Pfeiifer), Elsevier Publ. Co., New York, N. Y. (1950), pages -141 relied on. 

1. IN THE OXIDATION OF A PETROLEUM ASPHALT BY BLOWING THE ASPHALT WITH AIR IN THE PRESENCE OF FERRIC CHLORIDE, THE IMPROVEMENT WHICH COMPRISES EXTRANEOUSLY LIQUEFYING FECI3.6H2O BY HEATING IT ABOVE ITS CONGRUENT MELTING POINT AND ADDING UP TO ABOUT 1 WEIGHT PERCENT OF THE RESULTING LIQUID TO THE ASPHALT BEING OXIDIZED. 